Calcining coke



Feb. 22, 1966 w. J. METRAILER CALCINING COKE Filed July 12. 1962 William Joseph Merroiler Inventor Bil 1.

Potent Ahorney United States Patent 3,236,745 CALCINING COKE William Joseph Metrailer, Baton Rouge, La., assignor to Essa Research and Engineering Company, a corporation of Delaware Filed July 12, 1962, Ser. No. 209,415 5 Claims. (Cl. 20131) This invention relates to calcining fluid coke and more particularly relates to calcining coke withdrawn from the coke burner vessel and passing the coke down through a vertically arranged calcining zone countercurrent to upflowing gas.

The coking of heavy hydrocarbon oils such as heavy crude oils, residual oils, vacuum still residues, tars, pitches, etc., to produce fuel products such as gasoline and gas oil, or for the production of chemical raw materials, such as aromatics, olefins, diolefins, etc., also produces petroleum coke. The amount of coke produced depends on the character of the oil feed stock and to some extent upon the coking conditions.

One of the major uses to which petroleum coke has been put has been the manufacture of electrodes therefrom. However, the petroleum coke can be used for making other shaped bodies such as carbon blocks, etc. Green or uncalcined coke contains volatile material which must be removed before the coke is suitable for many uses. In some cases the coke contains a large percentage of sulfur which is undesirable. Calcining is accomplished by heating the coke to a relatively high temperature of at least about 1800 F. The calcining operation reduces the volatile content of the coke, raises the real density of the coke and reduces the electrical resistivity. At the higher temperatures there is also a reduction in the sulfur content of the coke.

The commercial fluid coking process differs from the delayed coking process and produces substantially spherical fluid coke particles which also differ from the coke made in the delayed coking process. The fluid coking process has been described in published articles and patents and attention is directed to Preiffer et a1. Patent 2,881,130 granted April 7, 1959. The desecription in the Pfeifl'er et al. patent is incorporated herein by reference thereto.

Heavy hydrocarbon oil feeds suitable for fluid coking include heavy crude oils, atmospheric and vacuum bottoms, pitch, asphalt, residual oils, tars, etc., or mixtures thereof. Such oil feeds can have an initial boiling point of about 700 F. or higher, an API gravity between about and 5 and a Conradson Carbon residue content of between about 5 and 40 wt. percent.

The fluid coking unit consists basically of a reaction vessel or coker and a burner vessel. In a typical operation the heavy oil to be processed is injected into the reaction vessel containing a fluidized bed of inert solid particles, preferably coke particles, maintained at a temperature between about 850 F. and 1200 F. and preferably between about 950 F. and 1050 F. for the production of fuels or at a higher temperature, e.g. 1200 F. to 1600 F. for the production of chemicals, i.e. aromatics and olefins. Substantially uniform temperature exists in the coking bed.

Uniform mixing in the bed results in virtually isothermic conditions and effects substantially instant distribution of the feed stock. In the reaction zone the feed stock is partially vaporized and partially cracked. Product vapors are removed from the coking vesel and sent to a fractionator for the recovery of gas and light distil lates therefrom. Any heavy bottoms are usually returned to the coking vessel. The coke produced in the process remains in the bed coated on the solid particles thereof.

The heat for carrying out the endothermic coking reaction is generated in the burner vessel. A stream of coke or coke-coated solid inert particles, if the latter are used, is transferred from the reactor to the burner vessel employing a standpipe and riser system. Air and/or steam is supplied to the riser for conveying the solids to the burner. Sufiicient coke or carbonaceous matter is burned in the burner vessel to bring the solids therein up to a temperature sufiicient to maintain the system in heat balance.

The burner solids are maintained at a higher temperature than the solids in the reactor. About 5% of coke on the feed is burned for this purpose. This amounts to approximately 15% to 30% of the coke made in the process. The unburned portion of the coke represents the net coke formed in the process. This coke is preferably withdrawn from the burner vessel, normally cooled and sent to storage. The coke normally contains about 86% to 94% carbon, 1.5% to 2% hydrogen, 0.5% to 7.5% sulfur, 0.6% to 1.5% volatile matter at 1100 R, up to 6% volatile matter at 950 C. and approximately 0.5% to 3.0% ash.

According to the present invention, coke made in the coking process is transferred continuously without quenching or cooling to a calcining operation. In the calcining operation the coke is subjected to high temperature, or high temperature and soaking, in order to remove volatile material therefrom to increase its true density and to lower its electrical resistivity.

The fluid coke particles normally produced in the fluid coking process have a particle diameter mostly, that is, about 60 to wt. percent, in the range of about 28 to 200 mesh, a sulfur content between about 1.0 and 6.0 wt. percent, a volatile content measured 950 C. between about 5.0 and 7.5 wt. percent. The coke particles have a real density between about 1.4 and 1.7 which is too low for use in the manufacture of carbon electrodes in making aluminum and for some other purposes. Increased density and lower sulfur and volatile content are particularly necessary to make the fluid coke suitable for use in the manufacture of electrodes. By calcining the fluid coke at a temperature above about 2000 F. and for a selected time, the density of the coke particles is increased and the volatile content and sulfur are reduced.

According to the present invention fluid coke particles are withdrawn directly from the lower portion of the dense fluidized bed of solids in the burner vessel and introduced into the upper portion and below the top or upper end of a vertically arranged elongated calcining vessel provided with vertically spaced baflles or holdup trays or means to provide staged heating. The coke particles fall or rain down the calcining vessel countercurrent to upflowing hot gases. Hot combustion gases and/or oxygencontaining gases such as air are introduced at vertically spaced points along the length of the calcining vessel to provide a disperse phase of solids in the calcining vessel. The baflies assure good contacting between the upflowing hot gas and downflowing coke particles between the stages of gas injection and also control the rate of heating up of the coke particles.

The upper end of the calcining vessel acts as an elutriating zone to separate fines and return them to the unit. The process is integrated with the coke burner vessel and the hot gases and fines leaving the top of the calcining vessel are passed directly into the burner vessel with suflicient contacting in the fluid bed in the coke burner vessel to recover heat from the gases and fines. The coke fines from the calcining vessel are recovered along with the fines from the coke burner or heating vessel.

The process is carried out so that the net coke formed is the coke product withdrawn from the process. The calcining vessel is operated to provide elutriation of the 3 fine fluid coke in the early stages of the calcining treatment so that only the desired coarse coke particles reach the final calcining temperature at or near the bottom portion of the calcining vessel from which the calcined coarse fluid coke particles are withdrawn and cooled or quenched in any suitable or conventional manner.

According to the present invention, fluid coke particles are calcined by employing the raining solids technique in the major portion of a vertically arranged elongated calcining vessel or zone and staged heating is obtained by spaced heat injection means with baffles provided at spaced vertical points to provide staging. The calcining zone is integrated with the fluid coker burner vessel so that fluid coke passes directly from the burner vessel to the upper portion but below the top of the calcining zone or vessel and the hot gases and coke fines pass directly from the top of the calcining zone or vessel into the dense fluid turbulent bed of coke particles in the coker burner vessel.

In the drawing, the figure diagrammatically.represents one form of apparatus adapted to be used in carrying out the process of the present invention.

Referring now to the drawing, the reference character 10 designates a vertically arranged cylindrical fluid coker burner vessel provided with a dense fluidized turbulent bed 12 of coke particles having a level indicated at 14. Hot fluid coke particles from the fluid coker reactor vessel (not shown) are passed through line 16 into the bottom portion of the burner vessel 10. Heated fluid coke particles for recycle to the fluid coker reactor vessel are withdrawn from the dense fluidized bed 12 through line 18. Some of the coke may be withdrawn as product coke from line 16 or line 18 but is preferably withdrawn from line 18, cooled and sent to storage. Or all the excess coke which is not necessary for supplying heat for the coking step is calcined according to the present process to provide calcined coke product.

The burner vessel 10 is provided with line 22 which communicates with the bottom portion of the fluid coke bed 12 in burner vessel 10 for supplying air or cmbustion supporting oxygen-containing gas to burn part of the fluid coke particles in burner vessel to heat the coke particles which are to be recycled to the coker reactor vessel through line 18 to supply the heat of cracking or coking in the coking step. Instead of air, hot combustion gases may be supplied through line 22. The quantity of oxygen and/or combustion gases supplied to line 22 is adjusted to take care of incremental heat requirements above that recovered from the calciner. The air and combustion gases pass upwardly through burner vessel 10 at a superfical velocity between about 0.5 and 5.0 ft./ sec. to maintain the coke particles as a dense turbulent fluid bed as shown at 12 in the burner vessel 10.

Gases containing entrained fine coke particles leave the dense bed 12 and pass upwardly to the dilute or disperse phase 24 above the level 14 of bed 12 and are passed through one or more solids-separating devices shown as a cyclone separator 26 arranged within burner vessel 10 at the top thereof and provided with a dip leg 28 for returning separated coke solids to the dense bed 12. Cyclone separator 26 has gas outlet line 32 for removing separated hot flue gas which can be sent to a waste heat boiler or for other energy recovery means and then to the stack.

The burner vessel is operated at a temperature between about 1100 F. and 1400" F. for fuel production and proportionately higher for production of chemicals when the reactor vessel is at a higher temperature. The temperature of the coke solids in burner vessel 10 is usually about 150 F. to 300 F. higher than that of the solids in the coker reactor vessel.

The fluid coke particles to be calcined are withdrawn directly from the bottom of the fluid bed 12 in the burner vessel 10 through line 33 and passed into the upper end of a vertically arranged elongated calcining vessel 34 circular in cross section and which extends through the bottom of burner vessel 10 and up into the burner vessel 10 and is submerged in the dense fluid bed 12. The diameter of the vessel 34 is much smaller than than that of the burner vessel 10, normally about A that of vessel 10. The upper end 36 of calcining vessel 34 is arranged to be below the level 14 of the dense fluid bed 12 in burner vessel 10. Line 33 has its inlet end below the top 36 of calcining vessel 34. In this way the upper portion 37 of vessel 34 upwardly from the inlet of line 33 functions as an elutriator to separate fines or fine coke from coarse coke and to return the fine coke to the fluid bed 12 in the burner 10.

The upper end 36 of calcining vessel 34 is open. A baflle 38 is arranged above and in spaced relation to the upper open end 36 of calcining vessel 34 to change the direction of flow of gases and fine solids suspension leaving the top of calcining vessel 34 and cause them to first flow down and then up to be redistributed in the dense bed 12 before being passed up and out of the burner vessel 10. This improves contacting between the hot gases and fine coke from the calciner and the coke in the dense fluid bed burner. The baffle 38 is in the form of an inverted flanged circular disc U-shaped in cross section and of a larger diameter than the diameter of the top of the calcining vessel 34.

A level control device diagrammatically shown at 42 is provided to maintain the level 14 of the fluidized solids bed in burner vessel 10 approximately as shown in the drawing and at a higher level than the outlet end 36 of calcining vessel 34 and also above the bafile 38. The level control device controls the flow of solids into the calcining vessel through line 33. If the level 14 becomes too high the level control device 42 actuates valve 44 in line 33 leading from the bottom of burner vessel 10 and communicating with calcining vessel 34 at a region below the bottom of vessel 10 to introduce coke particles into the upper portion of calcining vessel 34 but below the upper open end 36 thereof.

The coke particles to be calcined are introduced into the upper portion but below the top of the calcining vessel 34 through line 33 and pass down through the major portion of calcining vessel 34 in a falling or raining solids manner countercurrent to upflowing hot gases which are introduced at a plurality of points along the length of the calcining vessel 34. The coke particles are calcined at a temperature between about 1800 F. and 3000 F. preferably between about 2100 F. and 2700 F. The total holding time during calcining is in the range between about 0.2 and 20 hours and preferably between about 0.3 and 12 hours.

The lower outlet end 42 of calcining vessel 34 is provided with a valve 45 for controlling the withdrawal of calcined coke. The lower portion 42 of calcining vessel 34 above the valve-45 .is used as a soaking section and the calcined coke is collected here as a dense non-fluid or downwardly moving bed 46 with a superimposed fluidized solid-bed 48. As coke is withdrawn from the bottom of bed 46, the coke moves down in the bed 46 and also some coke particles move down from the fluid bed 48 into the non-fluid or moving bed.

The calcining vessel 34 is preferably provided along y its length and at its intermediate portion with spaced bafiles or holdup trays 52 to provide stage heating and improved contacting between the upflowing gases and downflowing coke solids. The trays are shown arranged in pairs but other arrangements may be used. These baflles are shown as portions of an ellipse and each baflle is arranged at an acute angle with the vertical inside wall of vessel 34. These batfles are preferably installed at the middle portion of the calcining vessel 34. Hot combustion gases or combustion supporting gases are introduced at spaced regions through a plurality of lines 54, 56, 58, 62 and 64 for supplying heat for the calcination step.

The top line 54 introduces hot combustion gases or an oxygen-containing gas into the upper portion of the calcining vessel 34 above the top pair of baflies 52 and below the upper end 36 of calcining vessel 34. The next lower line 56 for introducing hot combustion gases or combustion supporting gas or gases is preferably arranged about halfway between the top pair of baflles 52 and the next lower pair of baffles 53. The next lower line 58 for introducing gases is preferably arranged between the bottom pairs of bafiles 53 and 53'. Line 62 is provided for supplying hot combustion gases or combustion supporting gases into the calcining vessel 34 below the bottom pair of batfles 53'. Line 64 is provided for introducing hot combustion gases or combustion supporting gas below line 62 to form the relatively shallow fluid bed 48 which is provided to assure that all of the coke has reached the desired final calcining temperature. If desired, fluid bed 48 may be omitted.

Line 66 is provided at the bottom portion of calcining vessel 34 above valve 45 for introducing a treating gas int-o the bottom portion of dense non-fluid or moving bed 46. This treating gas may be air, hydrogen, combustion gases, natural gas, methane or the like.

The calcining vessel 34 is especially adapted for calcining fluid coke particles in the disperse phase. Lines 54, 56, 58, 62, 64 and 66 are provided at spaced intervals for the introduction of hot combustion gases or oxygen-containing gas such as air. Where the coke is a valuable end product, fuel such as natural gas is burned in a suitable burner to produce h-ot combustion gases which are used to heat up the coke particles to calcining temperatures. These hot combustion gases are passed through lines 54, 56, 53, 62, 64 and 66.

Where the coke is not as valuable an end product or where it is desired to burn part of the coke particles passing through the calcining vessel 34, a combustion supporting gas such as air or preheated air is passed through lines 54, 56, 58, 62, 64 and 66 to burn part of the coke to raise the coke particles to calcining temperatures. Or a combination of hot combustion gases in one portion of vessel 34 and oxygen-containing gas in another portion may be used.

The invention is not to be limited to the number or type of baflies used. Coke is calcined in the calcining vessel 34 in a dilute or disperse phase extending from about the region of discharge of line 33 into the upper portion or" vessel 34 down below battles 53' and to the top of fluid bed 48 and most of the heat is supplied to the coke particles in this portion of the calcining vessel 34. The rest or between about 5 and 25 of the total heat input is introduced into the fluid bed 48 where the final calcining temperature is reached.

From the fluid bed 48 the coke particles at calcining temperature pass to the non-fluid or dense downwardly moving compact bed 46 where the coke particles are held for a suflicient time to assure complete calcination. Treating of the coke particles with hydrogen or densification with gaseous hydrocarbons such as methane or natural gas may be accomplished in compact bed 46 by introducing the hydrogen or hydrocarbon gas into the bottom portion of compact bed 46 through line 66.

Where methane or natural gas is introduced into compact bed 46, the cracking of the hydrocarbon not only deposits coke on the coke particles and makes them more dense but the cracking being endothermic also has a cooling effect on the coke particles and reduces the temperature of the coke particles to between about 1500 F. and 1800 F. Further cooling or quenching of the calcined and treated coke particles is necessary after withdrawing them from the bottom of calcining vessel 34.

The sections or portions of the calcining vessel set off by the pairs of bafiles 52 and designated 74, 76 and 78 form heating stages to control the rate of heating up of the coke particles and also to assure good contacting between the coke particles and the gases. The calcining 6 vessel 34 is shown as having a uniform diameter but the diameter of the various sections 37, 74, 76, 78, and the bottom section of vessel 34 above valve 44 may be different if needed to obtain the desired gas solids and holding times.

The coke particles at a temperature between about 1100 F. and 1400 F. are passed from the dense fluid bed 12 in burner vessel 10 through line 33 into the upper portion 37 of vertically arranged calcining vessel 34 but below the open upper end 36 thereof and as they fall or rain down through the calcining vessel 34, they are heated by the upflowing hot gases and their temperature is increased until they attain a calcining temperature at the bottom of the calcining vessel 34.

Assuming that air is introduced int-o the calcining vessel 34 through all the lines 54, 56, 58, 62 and 64, the velocity of the upflowing gases in top section 37 will be the highest and this section will act as an elutriator to elutriate fines or fine fluid coke in the upper portion 37 of calcining vessel 34 and returning them to burner vessel 10 so that only the desired coarse coke particles reach the final calcining temperature. Some of the coke is burned by air introduced through line 54 to heat the coke particles. Further heat is added by the hot gases flowing up from the lower hotter sections 74, 76 and 78. The temperature in the top section 37 is between about 1200 and 1700 F.

The superficial velocity of the upflowing gas in section 37 is between about 5 and 15 feet/ second and the density of the disperse phase or suspension in section 37 is between about 0.4 and 4.0 pounds per cubic foot.

Additional air is introduced through line 56 into the top calcining section 74 into which fluid coke is introduced through line 33 from burner 10. Section 74 is arranged between the top pairs of baflies 52 and 53 to heat the coke particles and to raise their temperature to between about 1300 F. and 1700 F. The superficial velocity of the gas passing up through section 74 is between about 4 and 14 feet/second and the density of the disperse phase or suspension of coke particles in gas is between about 0.35 and 3.5 pounds per cubic foot.

Air is introduced through line 58 into the next lower section 76 between the next lower pairs of battles 53 and 53' to heat the downflowing or downwardly moving coke particles to burn some of the particles and raise their temperature to between about 1400 F. and 1800" F. The superficial velocity of the gas passing up through section '76 is between about 3 and 10 feet/second and the density of the disperse phase of dilute suspension of coke particles in gas in section 76 is between about 0.1 and 3.0 pounds per cubic foot.

Additional air is introduced into next lower section 78 of the calcining vessel 34 through line 62 and below the lowermost pair of battles 53' to heat the coke particles and raise their temperature to between about 1600 F. and 2000 F. The superficial velocity of the gas passing up through section 78 is between about 2.5 and 9.0 feet/ second and the density of the dispersion or suspension of coke solids in gas in section 78 is between about 0.25 and 3.5 pounds per cubic foot.

Additional air is introduced through line 64 into the bottom section below section 7 8 and into the shallow fluid bed 48 to heat the coke and to obtain good mixing and contacting of the coke particles and gas and to assure that all the coke particles have reached the desired final calcining temperature between about 1600 F. and 2200 F. The dilute phase above fluid bed 48 has a density between about 0.2 and 3.0 pounds per cubic foot and is about the same temperature as the fluid coke particles in bed 48. The superficial velocity passing up through fluid bed 48 is between about 2.0 and 8.0 feet/second. About 5 to 25% of the total heat input to the calcining vessel 34 is introduced into fluid bed 48.

The hot coke particles are then passed from fluid bed down into the moving bed or non-fluid bed 46 where the coke particles are held for a suflicient time between about 0.2 and hours to assure complete calcination.

The coke particles in non-fluid bed 46 may be treated with hydrogen, if desired, to remove sulfur and thus hydrogen or hydrogen-containing gas is introduced through line 66 to pass up through the moving bed 46 at a superficial velocity between about 0.1 and 1.0 foot/second.

Where the coke particles in non-fluid bed 46 are completely calcined, they may be treated with natural gas or methane introduced through line 64 to crack these hydrocarbons and deposit coke on the coke particles to increase the density of the coke particles and generate hydrogen for the above treatment.

Instead of adding air alone through lines 54, 56, 58, 62 and 64, hot combustion gases alone, or in combination with air, as needed may be used.

As a result of the elutriation in the upper portion 37 of the calcination vessel 34, the calcined coke particles withdrawn from the bottom of the calcining vessel 34 through valve have a particle size mostly (60-90%) larger than about 48 mesh. The withdrawn coke particles have a volatile content of less than about 1.0 wt. percent, a real density greater than about 1.85 g./cc., and a sulfur content between about 1.0 and 4.0 wt. percent.

The method of heat introduction need not be the same at the various points of introduction of heat. Hot combustion gases may be introduced say into the fluid bed 48 and the hotter stage or stages of the calcining vessel 34 while combustion supporting gas like air may be introduced into the cooler upper stages to convert CO to CO and/or to burn volatile material or unoxidized or unburned fuel gases from the lower stages. During calcining, combustible gases including hydrogen and gaseous hydrocarbons are released and these can be burned in the calcining vessel 34.

The overhead gases and fine coke elutriated from the calcining vessel 34 leave the upper end 36 thereof and pass into coke bed 12 in coker burner vessel 10 with sufficient contacting to recover heat from the gases and fine coke. The gases and fine coke leaving the upper end 36 of calcining vessel 34 will usually be at a higher temperature than the fluid bed 12 of coke in burner vessel 10 and so heat will be transferred from the gases and fine coke to the coke particles in fluid bed 12. The elutriated fines are recovered along with the fines from the coker burner vessel 10 by cyclone separator system 26.

Part of the coke particles from line 16 may be passed from line 16 through valved line 82 directly to the top of the calcining vessel 34.

In a specific example where about 3800 barrels per day of residual petroleum oil having a gravity of about API, an initial atmospheric boiling point of about 850 F. and a Conradson carbon of about 25 wt. percent are coked in a fluid coking reactor at a temperature of about 900 F. and coke and vaporous cracked products are cooled, condensed and fractionated to obtain:

Gas, C minus tons/day C barrels/day 100 C 430 F do 500 43010l5 F. do 1900 Coke tons/day 180 Coke particle size in the range of about to 50 to 500 microns plus some 5 to 10% coke larger than 500 microns and up to 5000 microns or larger is circulated from the reactor to the burner.

The burner vessel 10 is about 12 feet in diameter and about 36 feet high in the cylindrical section. The calcining vessel 34 is about 14 feet long from the upper open end 36 to valve 45 and is about 3 feet in diameter.

About 24 tons of the coke per day are burned in vessel 10 to supply heat required for the coking step. The temperature in the burner vessel 10 is about 1110 F. The circulation rate between the reactor vessel (not shown) and burner vessel 10 is about 4.5 tons per minute.

About tons of net coke product are to be removed from the process and for the present example this is the coke to be calcined in vessel 34.

About 1300 tons of coke per day at a temperature of about 1120 F. are introduced into the upper portion 37 of calcining vessel 34 through line 33. About 1150 tons per day of this coke passes upward and returns to the burner. The remaining coke passes down countercurrently to gases passing up through lower section 74. About 200 mols of air per hour are introduced into elutriating section 37 through lines 54 and 56 to burn part of the coke particles. The air also burns combustible volatile material released from the coke in the lower portions of calcining vessel 34.

The superficial velocity of the gases passing up through top elutriating section 37 of calcining vessel 34 is about 10 feet/second and these gases include the air and combustion gases and the gases passing up from the lower sections of calcining vessel 34. The temperature in elutriating section 37 of calcining vessel 34 is about 1400 F. The fines comprising 0 to 400 micron coke particles are elutriated from the coke mixture introduced into the upper portion 37 of calcining vessel 34 through line 33 and pass up into the dense bed 12 in burner vessel 10.

The fines and hot gases passing to the burner vessel 10 give up heat to the fluid bed 12. in passing therethrough.

The density of the disperse phase of coke solids in section 37 is about 0.6 pound per cubic foot. The time of residence of the coke particles in section 37 is about 2 seconds.

The coke particles pass down from section 37 to section 74 in calcining vessel 34 where they are contacted with air introduced through line 56. The temperature of the coke particles in section 74 is about 1500 F. Some of the coke particles are burned along with volatile material released from the coke at the calcining temperatures in the lower part of calcining vessel 34 and passing up the calcining vessel 34. The density of the disperse phase in section 74 is about 0.2 pound per cubic foot. The time of residence of the coke particles in section 74 is about 5 seconds. The superficial velocity of the gases passing up through section 74 is about 7 feet/ second. The baffles 52, 53 and 53 in calcining vessel 34 effect good contacting between the coke particles and gas and also divide the vessel 34 into stages.

The coke particles pass down from section 74 into section 76 in calcining vessel 34 where they are contacted with air introduced through line 58. The temperature of the coke particles in section 76 is about 1650 F. Some of the coke particles and released volatile material is burned to increase the temperature of the coke particles passing down the calcining vessel 34. The density of the disperse phase or coke solids suspension in section 76 is about 0.3 pound per cubic foot. The time of residence of the coke particles in section 76 is about 5 seconds. The superficial velocity of the gases passing up through section 76 is about 6 feet/second.

The coke particles pass down into section 78 from section 76 in calcining vessel 34 where they are contacted with air introduced through line 62 to burn part of the coke particles and any released volatile combustible material. The temperature of the coke particles in section 78 is about 1800 F. The density of the disperse phase or suspension of coke particles in section 78 is about 0.3 pound per cubic foot. The time of residence of the coke particles in section 78 is about 5 seconds. The superficial velocity of the gases passing up through section 78 is about 5 feet/second.

A shallow bed of fluidized coke particles is provided at 48 in the bottom portion of section 78 superimposed on the compact, non-fluid coke particle bed 46. The bed 48 is about 3 feet deep and is at a temperature of about 2400 F. Air is introduced at the bottom of bed 48 through line 64- to provide fiuidizting gas at a superficial ve oc y f about 4 feet/second for fluidizing the 9 bed 48. The density of the fluid bed 43 is about pounds per cubic foot. The time of residence of the coke particles in bed 48 is about 200 seconds.

The coke particles then pass down into compact nonfluid bed 46 at the bottom of the calcining vessel 34 where it is contacted with a treating gas comprising natural gas. The temperature of the coke particles in bed 46 varies from about 2400 F. at the top to about 1500 F. at the bottom. The time of residence of the coke particles in bed 46 is about 2 hours. The coke particle size of the coke product is between about 200 and 5000 microns, whereas the coke particle size range of the particles returned to the burner vessel 10 is between about 50 and 500 microns.

Calcined coke particles are withdrawn from the bottom of calcining vessel 34 through valve at a temperature of about 1500' F. and are quenched with water to a temperature of about 350 F. The coke particles passing from the burner vessel It} to calcining vessel are compared to the calcined coke particles as follows:

What is claimed is:

1. A method of calcining coke particles produced in a fluid coking process which comprises removing hot coke particles including fine particles and coarse particles from the bottom portion of a fluid bed in a burner zone and passing said removed coke particles as a separate confined stream into the upper and elutriating portion but at a substantial distance below the open upper end of an elongated vertically arranged calcining zone which has only its open upper end arranged within said fluid bed in said burner zone, raining said coke particles down through said calcining zone, introducing an elutriating gas into the upper and elutriating portion of said calcining zone to remove coke fines from the coarse coke particles and to return the coke fines to said fluid bed in said burner zone, introducing air into said calcining zone at a plurality of vertically spaced regions along the length of said vertically arranged calcining zone for upward flow therethrough countercurrent to the falling or raining coke particles to produce a dilute dispersion of solids in gas and to burn part of the coke particles and volatile combustible material released from the coke at the higher calcining temperature further down in said calcining zone to increase the temperature thereof, increasing the calcining temperature in said calcining zone in a plurality of stages along the length of said elongated calcining zone as the coke particles pass down through said calcining zone to release volatile combustible material from said coke particles, removing calcined coarse coke particles from the bottom of said calcining zone as a downwardly moving compact, non-fluid bed and passing hot gases from the top of said upper elutriating portion of said calcining zone together with elutriated fine coke particles into said burner zone.

2. An apparatus for treating fluid coke particles which includes, in combination, a burner vessel having an inlet line for introducing coke particles and a withdrawal line for coke particles, a top gas outlet line, a second coke withdrawal line for withdrawing coke from the bottom of said burner vessel and communicating with the upper portion of a vertically arranged cylindrical calcining vessel hereinafter referred to, means for introducing a fluid- 7 izing gas into the lower portion of said burner vessel for fluidizing coke particles introduced into said burner vessel, said calcining vessel being of a smaller diameter than said burner vessel and extending downwardly from said burner vessel and extending up through the bottom of said burner vessel and into said burner vessel but terminating with an open upper end in said burner vessel intermediate the top and bottom thereof, said second coke withdrawal line communicating with the upper portion of said calcining vessel but below the top thereof and at a region exterior to and below said burner vessel for introducing coke particles into said calcining vessel for downward flow therethrough, a control valve at the bottom of said calcining vessel for controlling withdrawal of coke particles, and a plurality of vertically spaced inlet lines for introducing gas into said calcining vessel at vertically spaced regions for upward passage countercurrent to the downflowing coke particles and to heat said coke particles and to elutriate coke fines which are passed up into said burner vessel from the open upper end of said calcining vessel.

3. An apparatus according to claim 2 wherein a level control means is provided for maintaining a desired level of coke particles in said burner vessel, said control means being connected with said second coke withdrawal line for controlling the rate of withdrawal of coke particles through said second coke withdrawal line.

4. An apparatus for treating solid particles which includes, in combination, a first vessel having an inlet line for introducing solid particles and a withdrawal line for solid particles, a top gas outlet line, a second solids withdrawal line for withdrawing solids from the bottom of said first vessel and communicating with the upper intermediate portion of a vertically arranged cylindrical second vessel hereinafter referred to, means for introducing gas into the lower portion of said first vessel for fluidizing solid particles introduced into said first vessel, said second vessel being of a smaller diameter than said first vessel and extending downwardly from said first vessel and extending up through the bottom of said first vessel and into said first vessel and terminating with an open upper end in said first vessel intermediate the top and bottom thereof, said second solids withdrawal line communicating with the upper portion of said second vessel at a region exterior to and below said first vessel for introducing solid particles into said second vessel for downward flow therethrough, a control valve at the bottom of said second vessel for controlling withdrawal of solid particles, and a plurality of vertically spaced inlet lines for introducing gas into said second vessel at vertically spaced regions for upward passage countercurrent to the downfiowing solid particles and to elutriate fines which are passed up into said first vessel from the open upper end of said second vessel.

5. An apparatus according to claim 4 wherein a level control means is provided for maintaining a desired level of solid particles in said first vessel, said control means being connected with said second solids withdrawal line for controlling the rate of withdrawal of solid particles through said second solids withdrawal line.

References Cited by the Examiner UNITED STATES PATENTS 2,693,999 11/1954 Reed. 2,721,168 10/1955 Kimberlin et al. 20231 X 2,738,316 3/1956 Metrailer. 2,812,289 11/1957 Kimberlin.

MORRIS O. WOLK, Primary Examiner.

DELBERT E. GANTZ, Examiner. 

1. A METHOD OF CALCINING COKE PARTICLES PRODUCED IN A FLUID COKING PROCESS WHICH COMPRISES REMOVING HOT COKE PARTICLES INCLUDING FINE PARTICLES AND COARSE PARTICLES FROM THE BOTTOM PORTION OF A FLUID BED IN A BURNER ZONE AND PASSING SAID REMOVED COKE PARTICLES AS A SEPARATE CONFINED STREAM INTO THE UPPER AND ELUTRIATING PORTION BUT AT A SUBSTANTIAL DISTANCE BELOW THE OPEN UPPER END OF AN ELONGATED VERTICALLY ARRANGED CALCINING ZONE WHICH HAS ONLY ITS OPEN UPPER END ARRANGED WITHIN SAID FLUID BED IN SAID BURNER ZONE, RAINING SAID COKE PARTICLES DOWN THROUGH SAID CALCINING ZONE, INTRODUCING AN ELUTRIATING GAS INTO THE UPPER AND ELUTRIATING PORTION OF SAID CALCINING ZONE TO REMOVE COKE FINES FROM THE COARSE COKE PARTICLES AND TO RETURN THE COKE FINES TO SAID FLUID BED IN SAID BURNER ZONE, INTRODUCING AIR INTO SAID CALCINING ZONE AT A PLURALITY OF VERTICALLY REGIONS ALONG THE LENGTH OF SAID VERTICALLY ARRANGED CALCINING ZONE FOR UPWARD FLOW THERETHROUGH COUNTERCURRENT TO THE FALLING OR RAINING COKE PARTICLES TO PRODUCE A DILUTE DISPERSION OF SOLIDS IN GAS AND TO BURN PART OF THE COKE PARTICLES AND VOLATILE COMBUSTIBLE MATERIAL RELEASED FROM THE COKE AT THE HIGHER CALCINING TEMPERATURE FURTHER DOWN IN SAID CALCINING ZONE TO INCREASE THE TEMPERATURE THEREOF, INCREASING THE CALCINING TEMPERATURE IN SAID CALCINING ZONE IN A PLURALITY OF STAGES ALONG THE LENGTH OF SAID ELONGATED CALCINING ZONE AS THE COKE PARTICLES DOWN THROUGH SAID CALCINING ZONE TO RELEASE VOLATILE COMBUSTIBLE MATERIAL FROM SAID COKE PARTICLES, REMOVING CALCINED COARSE COKE PARTICLES FROM THE BOTTOM OF SAID CALCINING ZONE AS A DOWNWARDLY MOVING COMPACT, NON-FLUID BED AND PASSING HOT GASES FROM THE TOP OF SAID UPPER ELUTRIATING PORTION OF SAID CALCINING ZONE TOGETHER WITH ELUTRIATED FINE COKE PARTICLES INTO SAID BURNER ZONE. 